Invasive Species

What are invasive species?

Invasive species are species that are not native to our region. Not all non-native species are invasive though. For a species to be considered invasive, they would have a negative impact ecologically, socially or economically. They tend to grow rapidly, spread quickly and widely and can grow just about anywhere. Because these species did not evolve here, we don’t have the controls (insects, viruses, fungi, predators) that keep them in check in their own part of the world.

Under the BC Weed Control Act, all land owners have a regulatory responsibility to control designated noxious plants, as follows:

Duty to control noxious weeds:

In accordance with the regulations, an occupier must control noxious weeds growing or located on land and premises, and on any other property located on land and premises, occupied by that person.

Why are invasive species a problem?

Invasive species grow rapidly and are hard to get rid of, while out-competing native species. Because they arrive in Canada without their natural predators to keep them in balance, invasive plants and animals can spread rapidly. Specific threats include:

decreased biodiversity

altered water flow and leading to erosion and/or less available water

creating and increasing the fire hazard

damage to roads and other built structures

reduction of crop yield

recreational & tourism trails/areas choked by invasive monocultures

decreased property values

a loss of medicinal plants and cultural practices (loss of wild edibles, loss of habitat for wildlife and fish)

How do invasive species spread?

Improper disposal of garden waste

Although it might seem like a good idea to “recycle” your garden debris into a natural area, what you’re really doing is introducing plants that can smother, choke and otherwise ruin parks, greenways and other public greenspace needed by wildlife and used by people.

Unintentional dispersal (by direct growth)

Many invasive plants are rapid-growing and fast-spreading. English ivy, for example, can spread up to 4.5 metres in a single year.

Unintentional dispersal (by seed)

Many invasive plants are prolific seed producers. One purple loosestrife plant, for example, can produce 3 million seeds! These can then be dispersed by water, people, animals, vehicles, etc. to new areas.

Intentional introduction as garden ornamental

Many invasive plants got their start in someone’s garden. Most were exotics brought from other parts of the world. But here, they don’t have the same natural predators or checks to keep them under control and they literally go wild.

Are there invasive species in Squamish?

The District of Squamish’s highest priority invasive species are Japanese Knotweed, Giant Hogweed, and Yellow Flag Iris, all of which are on the BC Weed Control Act’s Noxious Weeds List.

These species grow and spread aggressively, are highly competitive, difficult to control, and can be highly destructive to natural resources, infrastructure, industry, and human health.

Their negative impacts are summarized here:

• Giant Hogweed causes severe burns to those who come into contact with it and may cause blindness.

• Japanese Knotweed damages infrastructure, reduces the structural integrity of dikes and streamside banks, accelerates erosion, impedes traffic sightlines, and devastates riparian systems. In the United Kingdom, the presence of Japanese Knotweed has now led to reduction of property value and refusal to mortgage.

• Yellow Flag Iris grows in water as dense thickets and blocks drainage.

Currently, there are more than 9 hectares of Japanese Knotweed on municipal land in the District of Squamish (based on 2010 data). Mapping shows that Japanese Knotweed and aforementioned species are spreading, and locations are increasing each year.

What is the District of Squamish doing?

The District of Squamish maintains representation on the board of regional Sea to Sky Invasive Species Council (SSISC), and contributes annually to the organization. These funds are successfully leveraged by SSISC to obtain additional funding, and used to develop programs that both benefit our community and provide direct support to District of Squamish staff to manage invasive species.

Some of the programs include the Japanese Knotweed Pesticide Control Program, the Invasive-Free Certification Program, Rebate Program for Invasive Plant Control on Private Land, and Community Weed Pulls.